1. Field of Invention
The present invention relates in general to automated guided vehicle (hereinafter, xe2x80x9cAGVxe2x80x9d) systems and methods for controlling the same, and more particularly, to an AGV system enabling communication between a central control device and an AGV so as to load and unload wafers one by one, and a method for controlling the same.
2. Description of Related Art
An AGV is one of factory automation facilities, and performs its tasks in predetermined places within a factory.
The AGV is generally comprised of a vehicle body of a rectangular box shape and a driver for driving the vehicle body. The driver is comprised of a plurality of driving wheels (not shown) installed to the lower portion of the vehicle body, driving the vehicle body, and a plurality of casters supporting the vehicle body. On one side of each driving wheel is mounted a wheel driving motor driving the driving wheel by means of a driving power supplied from a battery.
In a front part of the vehicle body is installed an obstacle sensor for sensing an obstacle. In front of the driving wheels are installed a pair of track sensors for sensing signals from objects to be sensed on a track. The AGV is comprised of an automated communicator for communication with an external central control device, and a controller controlling the respective wheel driving motors based on the signals from the obstacle sensor and the track sensor according to a command from the central control device received by the automated communicator.
An AGV for wafer transfer, as shown in FIG. 4, has a plurality of rest plates 65 and a robotic arm 55 installed on the top face of the vehicle body. A cassette 60 rests upon the rest plates 65, and a robotic arm 55 loads and unloads the cassette 60 on the rest plates 65.
The AGV 51 for wafer transfer travels along a facility line on which an inspector for inspecting the wafers is installed, and loads and unloads the cassette 60 to and from the inspector according to a command from the central control device. Generally, several inspectors of the same kind are disposed within a facility line, and therefore, each of the cassettes 60 loaded on the AGV 51 is transferred to each inspector 60. Each inspector inspects wafers contained in the cassette 60 if transferred, and transmits the inspection result and a signal indicating completion of the inspection to the central control device if the inspection of all the wafers is completed. The central control device determines based on the inspection result from each inspector whether each wafer is normal or not, and commands the AGV 51 to transfer the cassette 60 for the next process.
However, since the conventional AGV 51 transfers the cassette containing the wafers to the inspectors, the inspection result of each wafer cannot be obtained until all the wafers contained in the cassette 60 are inspected. Thus, it takes comparatively a long time to obtain the inspection result of the wafers. In addition, even when there is only a cassette to be inspected, since wafers within the cassette is to be inspected by an inspector, the other inspectors are in suspension until the inspection for all the wafers in the cassette 60 are finished, thereby lowering the efficiency in use of the inspectors and extending the inspection time.
To solve these problems, there has been developed an AGV having a transfer device provided with a single cassette and loading the wafers one by one on an inspector. In line with the development of such an AGV, there is a need of a new communication protocol system for communication between a central control device and an AGV to transfer the wafers one by one.
Accordingly, the present invention has been made keeping in mind the above-described shortcomings and need, and an object of the present invention is to provide an AGV system having a protocol system for communication between a central control device and an AGV so as to load and unload the wafers one by one, and a method for controlling the same.
This and other objects of the present invention may be achieved by a provision of an automated-guided vehicle (AGV) system comprising an AGV travelling on a facility line, having a vehicle body, a driver for driving the vehicle body and a transfer device for transferring a wafer to and from a cassette; and a central control device controlling an operation of the AGV, the central control device comprising a central communicator, communicating with the AGV according to a predetermined communication protocol, the AGV comprising a radio communicator, communicating with the central communicator according to the predetermined, communication protocol, and a controller activating the transfer device according to a command received by the radio communicator to transfer the wafer and controlling an operation of the driver.
The central control device transmits a load command to load the wafer in the AGV onto an equipment on the facility line, and the load command is comprised of at least one of a slot number of the wafer received within a slot of the cassette, a rotational position of the wafer, and an information as to whether a charge is given to the AGV.
Preferably, the central control device transmits a transfer command to transfer the wafer from the equipment on the facility line to the AGV, and the transfer command is comprised of at least one of a slot number of the wafer received within the slot of the cassette, a rotational position of the wafer, and information as to whether a charge is given to the AGV.
Preferably, the central control device transmits a command requesting to report an operation state of the AGV, the report command being comprised of at least one of an operation mode of the AGV, an operation state of the AGV, a load state of the wafer within the cassette and the consumed amount of a battery of the AGV.
According to another aspect of the present invention, this and other objects may be achieved by a method for controlling an AGV system comprising an AGV travelling on a facility line, having a vehicle body, a driver for driving the vehicle body and a transfer device for transferring a wafer to and from a cassette, and a central control device controlling an operation of the AGV, comprising the steps of transmitting a command according to a predetermined communication protocol from the central control device to the AGV; and activating the transfer device according to the command transmitted from the central control device to transfer the wafer and controlling an operation of the driver.
The command is comprised of at least one of a load command to load the wafer of the AGV onto the equipment on the facility line, a transfer command to transfer the wafer from the equipment to the AGV, and a command requesting to report an operation state of the AGV.
Preferably, the load command and the transfer command are respectively comprised of at least one of a slot number of the wafer received within the slot of the cassette, a rotational position of the wafer, and an information as to whether a charge is given to the AGV.
Desirably, the report command is comprised of at least one of an operation mode of the AGV, an operation state of the AGV, a load state of the wafer within the cassette and the consumed amount of a battery of the AGV.